The present application relates generally to combustion devices and, more particularly, to methods and systems for removing pollutants from an exhaust stream generated by the combustion devices.
During a typical combustion process within a furnace, for example, a flow of exhaust gases, or flue gases, is produced. Known exhaust gases contain combustion products including, but not limited to, carbon, fly ash, carbon dioxide, carbon monoxide, water, hydrogen, nitrogen, sulfur, chlorine, arsenic, selenium, and/or mercury.
Emissions from coal-fired power plants are subject to governmental regulation. At least some known pollutant control systems inject a sorbent, such as activated carbon, into the flow of flue gases to react with pollutants therein, such as mercury. Because carbon is more reactive with mercury at temperatures below 350° F., activated carbon is typically injected remotely from the combustion source. The injection location is also upstream from a particulate collection device, such as a baghouse. The activated carbon is retained within one or more filters positioned within the baghouse such that mercury is at least partially removed from the flue gases as the flue gases flow through and contact the activated carbon to react with the activated carbon.
During the operation of at least some known baghouses, the activated carbon is periodically removed to prevent the baghouse filters from becoming clogged with particulates. However, as the activated carbon is removed, mercury emissions may increase until additional activated carbon is introduced into the flow of flue gases. More generally, during such periods, the mercury emissions may increase above established regulatory limits during and/or after the baghouse filters have been cleaned, and before sufficient activated carbon has been reabsorbed by the baghouse filters.